1. Field of the Invention
This invention relates to method of recording radiographic images on a recording material by use of radiations such as X-rays, and more particularly to improvements in the method of recording radiographic images on a recording material by use of electrostatic latent images formed with charged particles emitted by a material which is irradiated with radiations having high energy such as X-rays, gamma rays and so forth.
2. Description of the Prior Art
It has been known in the art to use radiations for recording images of an object on a recording material. One of those methods employs an ordinary photographic film. Another method employs a xerographic photosensitive material which is exposed to X-rays after uniformly charged with electric charges to form an electrostatic latent image thereon. This method is called "xeroradiography" and is disclosed, for instance, in U.S. Pat. No. 2,666,144. The electrostatic latent image thus formed is developed on the recording material or developed after transferred to an insulating plate by use of toners as well known in the art.
Further, it has been known in the art, as disclosed in Japanese Patent Public Disclosure No. 48-82791/1973, to record images on a recording material by forming and developing an electrostatic latent image on an insulating recording material by ionizing a gas with X-rays and collecting ionized charges on the insulating recording material. This is called "ionography".
In addition, it has also been known in the art to record images on a recording material by forming and developing an electostatic latent image on an insulating recording material by irradiating a cathode of metal having a large atomic number with X-rays to cause the cathode to emit photoelectrons and collecting the photoelectrons on the insulating recording material disposed on an anode of metal having a small atomic number which is arranged in parallel to the cathode by applying an electric field across the cathode and anode. This method is called Reiss chamber method and is disclosed, for instance, in Japanese Patent Public Disclosure No. 49-95595 and a magazine of applied physics. i.e. Zeitschrift fur Angewandt Physik vol. 19, pages 1-4 (issued Feb. 19, 1965).
It is possible to apply a method as disclosed in U.S. Patent No. 2,900,515 to the above mentioned methods. In other words, an insulating recording layer of a recording material is first uniformly charged and then the charges carried on the recording layer are neutralized by charges having opposite polarity to that of the charges on the recording layer generated by the method of ionography or Reiss chamber. The image obtained by this method has a pattern reversed with respect to that obtained by the above mentioned methods.
Further, it is possible to combine the first two methods as suggested in Japanese Patent Public Disclosure No. 50-68340/1975. Japanese Patent Public Disclosure No. 50-33839/1975 shows a method wherein ions generated by irradiation of radiations are amplified by use of a micro-channel plate. Japanese Patent Public Disclosure No. 50-87793 shows a method wherein dielectric liquid is used as a substance to conduct photoelectric conversion.
The ionography and Reiss chamber method are advantageous over said xeroradiography in that the sensitivity thereof is several tens of times as high as that of the xeroradiography and these methods do not use expensive photosensitive materials. Further, these methods using a latent image formed on a recording material are advantageous over the conventional radiography using a photosensitive material in that the local contrast of the image obtained thereby is much higher than that of the image obtained by the radiography. Therefore, these methods are advantageous in obtaining diagnosis information in great detail.
However, these methods using an electrostatic latent image to be developed with toners are disadvantageous in that the gradation reproductibility of a high density part of the image is insufficient.
A detailed description of the above mentioned conventional methods will be made hereinbelow with reference to the drawing and the aforesaid disadvantages will be further explained in detail. Thereafter, the present invention will be described in detail. The method in accordance with the present invention uses the same recording device as that employed in the above methods such as the ionography and Reiss chamber method.